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Re: [mach1mach2cnc] Noise on Limit switches

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  • Simon Daykin
    Guys, Many thanks for the replies... Sorry, I didn t think to post the links to the actual piece of kit. I was thinking along the lines of general try this
    Message 1 of 12 , Sep 3, 2011
    • 0 Attachment
      Guys,

      Many thanks for the replies...

      Sorry, I didn't think to post the links to the actual piece of kit. I was
      thinking along the lines of general "try this" kind of replies.
      These are the switches we are using...
      http://www.ia.omron.com/data_pdf/data_sheet/e2s_dsheet_csm462.pdf
      E2S-W22

      Thanks for the pointers on calculating the resistance value.

      Simon


      ----- Original Message -----
      From: "John Dammeyer" <johnd@...>
      To: <mach1mach2cnc@yahoogroups.com>
      Sent: Friday, September 02, 2011 10:14 PM
      Subject: RE: [mach1mach2cnc] Noise on Limit switches


      > As usual, helping based on inadequate information is at best difficult.
      > Life is easier if the model number and even a link to the data sheet is
      > posted along with the request for help.
      >
      > Here's what I found.
      >
      > http://www.ia.omron.com/data_pdf/data_sheet/e2em_dsheet_csm448.pdf
      >
      > The two wire circuit may not ever pull brown and blue lines close enough
      > together to create a TTL logic low. The correct way to use such a switch
      > is to use it to close a relay or run current through an opto isolated
      > input. With 24V taking into account the opto LED voltage drop of about 1V
      > and the 'residual' voltage of 5V and assuming you want 20mA through the
      > opto-isolator device you'd use a load resistor of about 18V/0.02A = 900
      > Ohms.
      >
      > John Dammeyer
      >
      >
      >
      > Automation Artisans Inc.
      > http://www.autoartisans.com/ELS/
      > Ph. 1 250 544 4950
      >
      >
      >> -----Original Message-----
      >> From: mach1mach2cnc@yahoogroups.com
      >> [mailto:mach1mach2cnc@yahoogroups.com] On Behalf Of chuck
      >> Sent: Friday, September 02, 2011 12:18 PM
      >> To: mach1mach2cnc@yahoogroups.com
      >> Subject: Re: [mach1mach2cnc] Noise on Limit switches
      >>
      >>
      >> Simon,
      >> fyi what you are seeing is not noise. if your using 2 wire
      >> prox switches your seeing the current required to operate the
      >> circuit in the switch.
      >> as far as a pull down resister you need to look at the
      >> current the switch can handle and calculate the resistance to
      >> draw much less than that but low enough to pull the voltage
      >> at the controller below the trigger threshold.
      >> make sure you put the resister across the control input and
      >> not the switch.
      >> I'm sure one of the electronic gurus will explain it better....
      >> Chuck
      >>
      >>
      >> ----- Original Message -----
      >> From: Simon Daykin
      >> To: mach1mach2cnc@yahoogroups.com
      >> Sent: Friday, September 02, 2011 3:01 PM
      >> Subject: [mach1mach2cnc] Noise on Limit switches
      >>
      >>
      >>
      >> Guys,
      >>
      >> I am after some things to try with some limit switches...
      >>
      >> We are experiencing noise on an OMRON 2 wire 24v proximity switch.
      >> When switched, the "switched" voltage is still around 4v
      >> and this is is still activating the controller. The noise if
      >> believed to be picked up on the cables (they are very long
      >> but are shielded)
      >> All the power supplies are all 0v referenced together.
      >> The shields are all ok.
      >> We have tried to put a small capacitor to act as a filter
      >> but it did not help.
      >> The next thing to try is a pull-down resistor but I am
      >> unsure as to what resistance I would need.
      >>
      >> Any other suggestions?
      >>
      >> Thanks
      >> Simon
      >>
      >> [Non-text portions of this message have been removed]
      >>
      >>
      >>
      >>
      >>
      >> [Non-text portions of this message have been removed]
      >>
      >>
      >>
      >> ------------------------------------
      >>
      >> www.machsupport.com - Web site AccessYahoo! Groups Links
      >>
      >>
      >>
      >>
      >
      >
      >
      > ------------------------------------
      >
      > www.machsupport.com - Web site AccessYahoo! Groups Links
      >
      >
      >
    • John Dammeyer
      That device is TTL compatible. It should bring the signal low. I d wire it like this: 470R +12V --- / / /----|-----------BROWN-------[ ] ... LIMIT IN
      Message 2 of 12 , Sep 3, 2011
      • 0 Attachment
        That device is TTL compatible. It should bring the signal low.

        I'd wire it like this:
        470R
        +12V ---\/\/\/----|-----------BROWN-------[ ]
        | [ ]
        LIMIT IN ---------| [ ]SENSOR E2S-W22
        [ ]
        GND --------------------------BLUE--------[ ]

        Or 900R with 24V. That gives you about 20mA flowing through the wires
        which makes it fairly noise immune. The larger the resistor, the lower
        the current and the more likely noise can be coupled onto the wires.
        Ideally they should be a twisted pair so that common mode signals are
        cancelled out.

        John Dammeyer

        Automation Artisans Inc.
        http://www.autoartisans.com/ELS/
        Ph. 1 250 544 4950


        > -----Original Message-----
        > From: mach1mach2cnc@yahoogroups.com
        > [mailto:mach1mach2cnc@yahoogroups.com] On Behalf Of Simon Daykin
        > Sent: Saturday, September 03, 2011 2:40 AM
        > To: mach1mach2cnc@yahoogroups.com
        > Subject: Re: [mach1mach2cnc] Noise on Limit switches
        >
        >
        > Guys,
        >
        > Many thanks for the replies...
        >
        > Sorry, I didn't think to post the links to the actual piece
        > of kit. I was
        > thinking along the lines of general "try this" kind of replies.
        > These are the switches we are using...
        > http://www.ia.omron.com/data_pdf/data_sheet/e2s_dsheet_csm462.pdf
        > E2S-W22
        >
        > Thanks for the pointers on calculating the resistance value.
        >
        > Simon
        >
        >
        > ----- Original Message -----
        > From: "John Dammeyer" <johnd@...>
        > To: <mach1mach2cnc@yahoogroups.com>
        > Sent: Friday, September 02, 2011 10:14 PM
        > Subject: RE: [mach1mach2cnc] Noise on Limit switches
        >
        >
        > > As usual, helping based on inadequate information is at
        > best difficult.
        > > Life is easier if the model number and even a link to the
        > data sheet is
        > > posted along with the request for help.
        > >
        > > Here's what I found.
        > >
        > > http://www.ia.omron.com/data_pdf/data_sheet/e2em_dsheet_csm448.pdf
        > >
        > > The two wire circuit may not ever pull brown and blue lines
        > close enough
        > > together to create a TTL logic low. The correct way to use
        > such a switch
        > > is to use it to close a relay or run current through an
        > opto isolated
        > > input. With 24V taking into account the opto LED voltage
        > drop of about 1V
        > > and the 'residual' voltage of 5V and assuming you want 20mA
        > through the
        > > opto-isolator device you'd use a load resistor of about
        > 18V/0.02A = 900
        > > Ohms.
        > >
        > > John Dammeyer
        > >
        > >
        > >
        > > Automation Artisans Inc.
        > > http://www.autoartisans.com/ELS/
        > > Ph. 1 250 544 4950
        > >
        > >
        > >> -----Original Message-----
        > >> From: mach1mach2cnc@yahoogroups.com
        > >> [mailto:mach1mach2cnc@yahoogroups.com] On Behalf Of chuck
        > >> Sent: Friday, September 02, 2011 12:18 PM
        > >> To: mach1mach2cnc@yahoogroups.com
        > >> Subject: Re: [mach1mach2cnc] Noise on Limit switches
        > >>
        > >>
        > >> Simon,
        > >> fyi what you are seeing is not noise. if your using 2 wire
        > >> prox switches your seeing the current required to operate the
        > >> circuit in the switch.
        > >> as far as a pull down resister you need to look at the
        > >> current the switch can handle and calculate the resistance to
        > >> draw much less than that but low enough to pull the voltage
        > >> at the controller below the trigger threshold.
        > >> make sure you put the resister across the control input and
        > >> not the switch.
        > >> I'm sure one of the electronic gurus will explain it better....
        > >> Chuck
        > >>
        > >>
        > >> ----- Original Message -----
        > >> From: Simon Daykin
        > >> To: mach1mach2cnc@yahoogroups.com
        > >> Sent: Friday, September 02, 2011 3:01 PM
        > >> Subject: [mach1mach2cnc] Noise on Limit switches
        > >>
        > >>
        > >>
        > >> Guys,
        > >>
        > >> I am after some things to try with some limit switches...
        > >>
        > >> We are experiencing noise on an OMRON 2 wire 24v
        > proximity switch.
        > >> When switched, the "switched" voltage is still around 4v
        > >> and this is is still activating the controller. The noise if
        > >> believed to be picked up on the cables (they are very long
        > >> but are shielded)
        > >> All the power supplies are all 0v referenced together.
        > >> The shields are all ok.
        > >> We have tried to put a small capacitor to act as a filter
        > >> but it did not help.
        > >> The next thing to try is a pull-down resistor but I am
        > >> unsure as to what resistance I would need.
        > >>
        > >> Any other suggestions?
        > >>
        > >> Thanks
        > >> Simon
        > >>
        > >> [Non-text portions of this message have been removed]
        > >>
        > >>
        > >>
        > >>
        > >>
        > >> [Non-text portions of this message have been removed]
        > >>
        > >>
        > >>
        > >> ------------------------------------
        > >>
        > >> www.machsupport.com - Web site AccessYahoo! Groups Links
        > >>
        > >>
        > >>
        > >>
        > >
        > >
        > >
        > > ------------------------------------
        > >
        > > www.machsupport.com - Web site AccessYahoo! Groups Links
        > >
        > >
        > >
        >
        >
        >
        > ------------------------------------
        >
        > www.machsupport.com - Web site AccessYahoo! Groups Links
        >
        >
        >
        >
      • Simon Daykin
        John, Thanks for the wiring info, I need to double check how it is wired... The problem we are seeing is that the switch appears to be bringing the signal low
        Message 3 of 12 , Sep 3, 2011
        • 0 Attachment
          John,

          Thanks for the wiring info, I need to double check how it is wired...
          The problem we are seeing is that the switch appears to be bringing the signal low but then noise being picked up in the brown/blue shielded/twisted pair is raising the voltage at the "limit in" to around the 4.5v level.

          Thanks
          Simon

          > That device is TTL compatible. It should bring the signal low.
          >
          > I'd wire it like this:
          > 470R
          > +12V ---\/\/\/----|-----------BROWN-------[ ]
          > | [ ]
          > LIMIT IN ---------| [ ]SENSOR E2S-W22
          > [ ]
          > GND --------------------------BLUE--------[ ]
          >
          > Or 900R with 24V. That gives you about 20mA flowing through the wires
          > which makes it fairly noise immune. The larger the resistor, the lower
          > the current and the more likely noise can be coupled onto the wires.
          > Ideally they should be a twisted pair so that common mode signals are
          > cancelled out.
          >
          > John Dammeyer
          >
          > Automation Artisans Inc.
          > http://www.autoartisans.com/ELS/
          > Ph. 1 250 544 4950
          >
          >
          >> -----Original Message-----
          >> From: mach1mach2cnc@yahoogroups.com
          >> [mailto:mach1mach2cnc@yahoogroups.com] On Behalf Of Simon Daykin
          >> Sent: Saturday, September 03, 2011 2:40 AM
          >> To: mach1mach2cnc@yahoogroups.com
          >> Subject: Re: [mach1mach2cnc] Noise on Limit switches
          >>
          >>
          >> Guys,
          >>
          >> Many thanks for the replies...
          >>
          >> Sorry, I didn't think to post the links to the actual piece
          >> of kit. I was
          >> thinking along the lines of general "try this" kind of replies.
          >> These are the switches we are using...
          >> http://www.ia.omron.com/data_pdf/data_sheet/e2s_dsheet_csm462.pdf
          >> E2S-W22
          >>
          >> Thanks for the pointers on calculating the resistance value.
          >>
          >> Simon
          >>
          >>
          >> ----- Original Message -----
          >> From: "John Dammeyer" <johnd@...>
          >> To: <mach1mach2cnc@yahoogroups.com>
          >> Sent: Friday, September 02, 2011 10:14 PM
          >> Subject: RE: [mach1mach2cnc] Noise on Limit switches
          >>
          >>
          >> > As usual, helping based on inadequate information is at
          >> best difficult.
          >> > Life is easier if the model number and even a link to the
          >> data sheet is
          >> > posted along with the request for help.
          >> >
          >> > Here's what I found.
          >> >
          >> > http://www.ia.omron.com/data_pdf/data_sheet/e2em_dsheet_csm448.pdf
          >> >
          >> > The two wire circuit may not ever pull brown and blue lines
          >> close enough
          >> > together to create a TTL logic low. The correct way to use
          >> such a switch
          >> > is to use it to close a relay or run current through an
          >> opto isolated
          >> > input. With 24V taking into account the opto LED voltage
          >> drop of about 1V
          >> > and the 'residual' voltage of 5V and assuming you want 20mA
          >> through the
          >> > opto-isolator device you'd use a load resistor of about
          >> 18V/0.02A = 900
          >> > Ohms.
          >> >
          >> > John Dammeyer
          >> >
          >> >
          >> >
          >> > Automation Artisans Inc.
          >> > http://www.autoartisans.com/ELS/
          >> > Ph. 1 250 544 4950
          >> >
          >> >
          >> >> -----Original Message-----
          >> >> From: mach1mach2cnc@yahoogroups.com
          >> >> [mailto:mach1mach2cnc@yahoogroups.com] On Behalf Of chuck
          >> >> Sent: Friday, September 02, 2011 12:18 PM
          >> >> To: mach1mach2cnc@yahoogroups.com
          >> >> Subject: Re: [mach1mach2cnc] Noise on Limit switches
          >> >>
          >> >>
          >> >> Simon,
          >> >> fyi what you are seeing is not noise. if your using 2 wire
          >> >> prox switches your seeing the current required to operate the
          >> >> circuit in the switch.
          >> >> as far as a pull down resister you need to look at the
          >> >> current the switch can handle and calculate the resistance to
          >> >> draw much less than that but low enough to pull the voltage
          >> >> at the controller below the trigger threshold.
          >> >> make sure you put the resister across the control input and
          >> >> not the switch.
          >> >> I'm sure one of the electronic gurus will explain it better....
          >> >> Chuck
          >> >>
          >> >>
          >> >> ----- Original Message -----
          >> >> From: Simon Daykin
          >> >> To: mach1mach2cnc@yahoogroups.com
          >> >> Sent: Friday, September 02, 2011 3:01 PM
          >> >> Subject: [mach1mach2cnc] Noise on Limit switches
          >> >>
          >> >>
          >> >>
          >> >> Guys,
          >> >>
          >> >> I am after some things to try with some limit switches...
          >> >>
          >> >> We are experiencing noise on an OMRON 2 wire 24v
          >> proximity switch.
          >> >> When switched, the "switched" voltage is still around 4v
          >> >> and this is is still activating the controller. The noise if
          >> >> believed to be picked up on the cables (they are very long
          >> >> but are shielded)
          >> >> All the power supplies are all 0v referenced together.
          >> >> The shields are all ok.
          >> >> We have tried to put a small capacitor to act as a filter
          >> >> but it did not help.
          >> >> The next thing to try is a pull-down resistor but I am
          >> >> unsure as to what resistance I would need.
          >> >>
          >> >> Any other suggestions?
          >> >>
          >> >> Thanks
          >> >> Simon
          >> >>
          >> >> [Non-text portions of this message have been removed]
          >> >>
          >> >>
          >> >>
          >> >>
          >> >>
          >> >> [Non-text portions of this message have been removed]
          >> >>
          >> >>
          >> >>
          >> >> ------------------------------------
          >> >>
          >> >> www.machsupport.com - Web site AccessYahoo! Groups Links
          >> >>
          >> >>
          >> >>
          >> >>
          >> >
          >> >
          >> >
          >> > ------------------------------------
          >> >
          >> > www.machsupport.com - Web site AccessYahoo! Groups Links
          >> >
          >> >
          >> >
          >>
          >>
          >>
          >> ------------------------------------
          >>
          >> www.machsupport.com - Web site AccessYahoo! Groups Links
          >>
          >>
          >>
          >>
          >
          >
          >
          > ------------------------------------
          >
          > www.machsupport.com - Web site AccessYahoo! Groups Links
          >
          >
          >

          [Non-text portions of this message have been removed]
        • John Dammeyer
          That s because the wire has resistance between the resistor and the sensor. You ll have to give us more details. For example. What value resistor are you
          Message 4 of 12 , Sep 3, 2011
          • 0 Attachment
            That's because the wire has resistance between the resistor and the
            sensor. You'll have to give us more details. For example. What value
            resistor are you using and what power supply? What is LIMIT IN? And
            opto? A parallel port on a PC? A BOB with a TTL Buffer?

            Ideally if the wire had zero resistance you'd see 0.6V at the sensor and
            0.6V at the LIMIT IN pin. But if the wire and/or your connections had 470
            Ohms worth of resistance then LIMIT IN would be at about 6.6V if the
            supply was 12V.

            The whole picture is needed.

            >
            > John,
            >
            > Thanks for the wiring info, I need to double check how it is wired...
            > The problem we are seeing is that the switch appears to be
            > bringing the signal low but then noise being picked up in the
            > brown/blue shielded/twisted pair is raising the voltage at
            > the "limit in" to around the 4.5v level.
            >
            > Thanks
            > Simon
            >
            > > That device is TTL compatible. It should bring the signal low.
            > >
            > > I'd wire it like this:
            > > 470R
            > > +12V ---\/\/\/----|-----------BROWN-------[ ]
            > > | [ ]
            > > LIMIT IN ---------| [ ]SENSOR E2S-W22
            > > [ ]
            > > GND --------------------------BLUE--------[ ]
            > >
            > > Or 900R with 24V. That gives you about 20mA flowing
            > through the wires
            > > which makes it fairly noise immune. The larger the
            > resistor, the lower
            > > the current and the more likely noise can be coupled onto the wires.
            > > Ideally they should be a twisted pair so that common mode
            > signals are
            > > cancelled out.
            > >
            > > John Dammeyer
            > >
            > > Automation Artisans Inc.
            > > http://www.autoartisans.com/ELS/
            > > Ph. 1 250 544 4950
            > >
            > >
            > >> -----Original Message-----
            > >> From: mach1mach2cnc@yahoogroups.com
            > >> [mailto:mach1mach2cnc@yahoogroups.com] On Behalf Of Simon Daykin
            > >> Sent: Saturday, September 03, 2011 2:40 AM
            > >> To: mach1mach2cnc@yahoogroups.com
            > >> Subject: Re: [mach1mach2cnc] Noise on Limit switches
            > >>
            > >>
            > >> Guys,
            > >>
            > >> Many thanks for the replies...
            > >>
            > >> Sorry, I didn't think to post the links to the actual piece
            > >> of kit. I was
            > >> thinking along the lines of general "try this" kind of replies.
            > >> These are the switches we are using...
            > >> http://www.ia.omron.com/data_pdf/data_sheet/e2s_dsheet_csm462.pdf
            > >> E2S-W22
            > >>
            > >> Thanks for the pointers on calculating the resistance value.
            > >>
            > >> Simon
            > >>
            > >>
            > >> ----- Original Message -----
            > >> From: "John Dammeyer" <johnd@...>
            > >> To: <mach1mach2cnc@yahoogroups.com>
            > >> Sent: Friday, September 02, 2011 10:14 PM
            > >> Subject: RE: [mach1mach2cnc] Noise on Limit switches
            > >>
            > >>
            > >> > As usual, helping based on inadequate information is at
            > >> best difficult.
            > >> > Life is easier if the model number and even a link to the
            > >> data sheet is
            > >> > posted along with the request for help.
            > >> >
            > >> > Here's what I found.
            > >> >
            > >> >
            > http://www.ia.omron.com/data_pdf/data_sheet/e2em_dsheet_csm448.pdf
            > >> >
            > >> > The two wire circuit may not ever pull brown and blue lines
            > >> close enough
            > >> > together to create a TTL logic low. The correct way to use
            > >> such a switch
            > >> > is to use it to close a relay or run current through an
            > >> opto isolated
            > >> > input. With 24V taking into account the opto LED voltage
            > >> drop of about 1V
            > >> > and the 'residual' voltage of 5V and assuming you want 20mA
            > >> through the
            > >> > opto-isolator device you'd use a load resistor of about
            > >> 18V/0.02A = 900
            > >> > Ohms.
            > >> >
            > >> > John Dammeyer
            > >> >
            > >> >
            > >> >
            > >> > Automation Artisans Inc.
            > >> > http://www.autoartisans.com/ELS/
            > >> > Ph. 1 250 544 4950
            > >> >
            > >> >
            > >> >> -----Original Message-----
            > >> >> From: mach1mach2cnc@yahoogroups.com
            > >> >> [mailto:mach1mach2cnc@yahoogroups.com] On Behalf Of chuck
            > >> >> Sent: Friday, September 02, 2011 12:18 PM
            > >> >> To: mach1mach2cnc@yahoogroups.com
            > >> >> Subject: Re: [mach1mach2cnc] Noise on Limit switches
            > >> >>
            > >> >>
            > >> >> Simon,
            > >> >> fyi what you are seeing is not noise. if your using 2 wire
            > >> >> prox switches your seeing the current required to operate the
            > >> >> circuit in the switch.
            > >> >> as far as a pull down resister you need to look at the
            > >> >> current the switch can handle and calculate the resistance to
            > >> >> draw much less than that but low enough to pull the voltage
            > >> >> at the controller below the trigger threshold.
            > >> >> make sure you put the resister across the control input and
            > >> >> not the switch.
            > >> >> I'm sure one of the electronic gurus will explain it better....
            > >> >> Chuck
            > >> >>
            > >> >>
            > >> >> ----- Original Message -----
            > >> >> From: Simon Daykin
            > >> >> To: mach1mach2cnc@yahoogroups.com
            > >> >> Sent: Friday, September 02, 2011 3:01 PM
            > >> >> Subject: [mach1mach2cnc] Noise on Limit switches
            > >> >>
            > >> >>
            > >> >>
            > >> >> Guys,
            > >> >>
            > >> >> I am after some things to try with some limit switches...
            > >> >>
            > >> >> We are experiencing noise on an OMRON 2 wire 24v
            > >> proximity switch.
            > >> >> When switched, the "switched" voltage is still around 4v
            > >> >> and this is is still activating the controller. The noise if
            > >> >> believed to be picked up on the cables (they are very long
            > >> >> but are shielded)
            > >> >> All the power supplies are all 0v referenced together.
            > >> >> The shields are all ok.
            > >> >> We have tried to put a small capacitor to act as a filter
            > >> >> but it did not help.
            > >> >> The next thing to try is a pull-down resistor but I am
            > >> >> unsure as to what resistance I would need.
            > >> >>
            > >> >> Any other suggestions?
            > >> >>
            > >> >> Thanks
            > >> >> Simon
            > >> >>
            > >> >> [Non-text portions of this message have been removed]
            > >> >>
            > >> >>
            > >> >>
            > >> >>
            > >> >>
            > >> >> [Non-text portions of this message have been removed]
            > >> >>
            > >> >>
            > >> >>
            > >> >> ------------------------------------
            > >> >>
            > >> >> www.machsupport.com - Web site AccessYahoo! Groups Links
            > >> >>
            > >> >>
            > >> >>
            > >> >>
            > >> >
            > >> >
            > >> >
            > >> > ------------------------------------
            > >> >
            > >> > www.machsupport.com - Web site AccessYahoo! Groups Links
            > >> >
            > >> >
            > >> >
            > >>
            > >>
            > >>
            > >> ------------------------------------
            > >>
            > >> www.machsupport.com - Web site AccessYahoo! Groups Links
            > >>
            > >>
            > >>
            > >>
            > >
            > >
            > >
            > > ------------------------------------
            > >
            > > www.machsupport.com - Web site AccessYahoo! Groups Links
            > >
            > >
            > >
            >
            > [Non-text portions of this message have been removed]
            >
            >
            >
            > ------------------------------------
            >
            > www.machsupport.com - Web site AccessYahoo! Groups Links
            >
            >
            >
            >
          • Craig
            Ok, That s what we need. It doesn t appear the sensor would work if the sensor is connected either between your input pin and ground or the input pin and 12V.
            Message 5 of 12 , Sep 3, 2011
            • 0 Attachment
              Ok,
              That's what we need.

              It doesn't appear the sensor would work if the sensor is connected either between your input pin and ground or the input pin and 12V. It is possible to use it but will take some additional resistors.

              The reason is in the details of the specification.

              CASE1:
              Sensor connected between ground and the input pin:
              In this case a resistor is needed between +12 and junction of the sensor and input pin.

              The sensor can't be used directly into TTL logic because of two issues:


              First, in the sensing state (output open) the +12 pullup resistor would over voltage the TTL logic input. And second, the in the non-sensing state, the [Control Output Residual Voltage Spec] is 3 volts at 50ma -- way too high to be a valid logic Zero for TTL.

              Lowering the circuit current (ie a larger value of pullup)may lower this 3V down to a point it may work (be a valid logic zero) but it would not be good engineering practice since the voltage vs current is not specified.

              CASE2:
              The sensor is connected between +12 and the bob input pin with a pull down resistor between the input pin and ground.

              This has the same over voltage issue as CASE1 but doesn't. This could be solved with the proper zener diode to limit the voltage on the input pin. The only other issue is the [Leakage Current Speck] of .8Ma.
              This flows all the time and the pull down resisotr would need to overcome this residual current to get a valid logic zero.

              The BOB should have an opto-isolator or relay input to work with these sensors. With an Opto input the sensor can be wired between +12 and the anode of the opto or between the cathode of the opto and ground. A current limiting resistor is needed in the circuit in either case. It doesn't matter if the resistor is on the anode, cathode or between the sensor and +12 or the sensor and ground since this is a series circuit.


              For +12 V operation with an opto isolated input using a standard 20ma drive current use a 370 ohm 1/4 watt resistor and for 24V use a 970 ohms 1/2W resistor. (12 -1.6V -3V)/.020A = 370 ohms

              Even with an opto there is still an issue of the [Leakage Current Spec] of .8ma. This is current that flows all the time through the sensor, sensing or not. If the BOB uses good high gain opto isolators this is enough current to make them operate, a very subtle condition. To solve this add about a 125 ohm resistor across the anode to cathode of the opto isolator.

              Craig









              --- In mach1mach2cnc@yahoogroups.com, "Simon Daykin" <simon@...> wrote:
              >
              > Guys,
              >
              > I am after some things to try with some limit switches...
              >
              > We are experiencing noise on an OMRON 2 wire 24v proximity switch.
              > When switched, the "switched" voltage is still around 4v and this is is still activating the controller. The noise if believed to be picked up on the cables (they are very long but are shielded)
              > All the power supplies are all 0v referenced together.
              > The shields are all ok.
              > We have tried to put a small capacitor to act as a filter but it did not help.
              > The next thing to try is a pull-down resistor but I am unsure as to what resistance I would need.
              >
              > Any other suggestions?
              >
              > Thanks
              > Simon
              >
              >
              > [Non-text portions of this message have been removed]
              >
            • Brian Barker
              John, Great diagram! I wish I could do ASCII art like that ... every time I go to draw something like that I get frustrated and open up Paint :) Thanks Brian
              Message 6 of 12 , Sep 6, 2011
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                John,
                Great diagram! I wish I could do ASCII art like that ... every time I go
                to draw something like that I get frustrated and open up Paint :)

                Thanks
                Brian


                On 9/3/2011 11:35 AM, John Dammeyer wrote:
                > That device is TTL compatible. It should bring the signal low.
                >
                > I'd wire it like this:
                > 470R
                > +12V ---\/\/\/----|-----------BROWN-------[ ]
                > | [ ]
                > LIMIT IN ---------| [ ]SENSOR E2S-W22
                > [ ]
                > GND --------------------------BLUE--------[ ]
                >
                > Or 900R with 24V. That gives you about 20mA flowing through the wires
                > which makes it fairly noise immune. The larger the resistor, the lower
                > the current and the more likely noise can be coupled onto the wires.
                > Ideally they should be a twisted pair so that common mode signals are
                > cancelled out.
                >
                > John Dammeyer
                >
                > Automation Artisans Inc.
                > http://www.autoartisans.com/ELS/
                > Ph. 1 250 544 4950
                >
              • John Dammeyer
                Thanks Brian, Normally I don t do ASCII art either. But this one seemed easy. John Dammeyer
                Message 7 of 12 , Sep 21, 2011
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                  Thanks Brian,

                  Normally I don't do ASCII art either. But this one seemed easy.

                  John Dammeyer

                  > John,
                  > Great diagram! I wish I could do ASCII art like that ...
                  > every time I go
                  > to draw something like that I get frustrated and open up Paint :)
                  >
                  > Thanks
                  > Brian
                  >
                  >
                  > On 9/3/2011 11:35 AM, John Dammeyer wrote:
                  > > That device is TTL compatible. It should bring the signal low.
                  > >
                  > > I'd wire it like this:
                  > > 470R
                  > > +12V ---\/\/\/----|-----------BROWN-------[ ]
                  > > | [ ]
                  > > LIMIT IN ---------| [ ]SENSOR E2S-W22
                  > > [ ]
                  > > GND --------------------------BLUE--------[ ]
                  > >
                  > > Or 900R with 24V. That gives you about 20mA flowing
                  > through the wires
                  > > which makes it fairly noise immune. The larger the
                  > resistor, the lower
                  > > the current and the more likely noise can be coupled onto the wires.
                  > > Ideally they should be a twisted pair so that common mode
                  > signals are
                  > > cancelled out.
                  > >
                  > > John Dammeyer
                  > >
                  > > Automation Artisans Inc.
                  > > http://www.autoartisans.com/ELS/
                  > > Ph. 1 250 544 4950
                  > >
                  >
                  >
                  > ------------------------------------
                  >
                  > www.machsupport.com - Web site AccessYahoo! Groups Links
                  >
                  >
                  >
                  >
                • Brian Barker
                  Rub it in that I have no ASCII skills LOL
                  Message 8 of 12 , Sep 21, 2011
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                    Rub it in that I have no ASCII skills LOL

                    On 9/21/2011 12:25 PM, John Dammeyer wrote:
                    > Thanks Brian,
                    >
                    > Normally I don't do ASCII art either. But this one seemed easy.
                    >
                    > John Dammeyer
                    >
                    >> John,
                    >> Great diagram! I wish I could do ASCII art like that ...
                    >> every time I go
                    >> to draw something like that I get frustrated and open up Paint :)
                    >>
                    >> Thanks
                    >> Brian
                    >>
                    >>
                    >> On 9/3/2011 11:35 AM, John Dammeyer wrote:
                    >>> That device is TTL compatible. It should bring the signal low.
                    >>>
                    >>> I'd wire it like this:
                    >>> 470R
                    >>> +12V ---\/\/\/----|-----------BROWN-------[ ]
                    >>> | [ ]
                    >>> LIMIT IN ---------| [ ]SENSOR E2S-W22
                    >>> [ ]
                    >>> GND --------------------------BLUE--------[ ]
                    >>>
                    >>> Or 900R with 24V. That gives you about 20mA flowing
                    >> through the wires
                    >>> which makes it fairly noise immune. The larger the
                    >
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